Wax sealing composition



Patented May 12, 1942 WAX SEALING COMPOSITION Frederick Warde Padgett,Jackson Heights, N. 2., assignor to Moore & Munger, Piainfleld, N. J., afirm composed of George T. Kea'ting, Edward P. Snyder, and MurrayRushmore No Drawing.

Claims.

This invention relates to a new and improved waxed paper, to be used forwrapping foods and other products.

One of the objects of the invention is to coat or impregnate paper witha wax of improved sealing strength.

Application October 27, 1939, Serial N0. 301,615

Another object of the invention is to provide paper which has beencoated or impregnated with improved petroleum wax.

Other objects of my invention will be set to: th

-in the following description which-illustrates preferred embodimentsthereof, it being understood that the above statements of the objects ofmy invention is intended generally to ,explain the same without limitingit in any manner.

Petroleum wax has a high resistance to water vapor, and paper which hasbeen coated or impregnated with such wax, is highly effective inexcluding or retaining moisture from or in the product being wrapped. Agood example is waxed bread wrapper, consisting of a sulphite sheet of20 to 25 lbs. weight to the ream which has been waxed up to 33 to 37lbs. to the ream. In the manufacture, part of the. wax soaks into thepaper and part remains on the surface. Hence this sheet is typical. ofwhat is known as the'wet waxed sheet and it possesses self-sealingproperties under the application of heat which melts or softens the wax,and subsequent cooling which solidifies the wax.

The self-sealing is carried out in well-known continuous machines, whenthe paper is used for wrapping loaves of bread.

The sealing effectiveness, even for the petrole-- um waxes having atensile strength of four hundred pounds to the square inch, never hasbeen entirely satisfactory, especially for such paper as is used forwrapping soft products. Hence it is important that the sealing strengthbe increased above that of the fully refined petroleum wax or waxes.

I have found that the incorporation of small amounts of selected I. G."waxes and other .hard, polar substances into the usual fully refinedpetroleum wax or waxes increases both the tensile and sealing strength,but the latter in much greater percentage than the former. In additionto this improvement in self-sealing, the tendency of the waxed sheets to.stick together, known as blocking is decreased.

The "I. G." wax which I- prefer to use has a melting point of 176181 F.,an acid value of 15-20, an ester value of -155, and a light yellowcolor. It contains only about'8-10% of unsaponifiable matter. It isreadily saponified by dissolving soap and either caustic soda or causticpotash jointly in water, and adding the melted "I. G. wax to the boilingsolution, with vigorous stirring. Said I. G. wax can be melted in asolution of soap and caustic alkali in water, and additional boilingwater can be added slowly. Smooth emulsions can thus be formed. Themethod of making the I. G. types of wax is disclosed in British PatentNo. 368,425. The I. G. waxes which I prefer 'to use are known in themarket as I. G. Wax E and I. G. Wax B and they are described in BulletinG-47-1 issued by General- Dyestufi Corporation of 230 5th Avenue, NewYork, N. Y. In said Bulletin the E wax is stated to have an acid valueof 15-20, and an ester value of 140-155; the B wax is stated to have anacid value of 10-60 and an ester value of 125-150.

Other I. G. waxes are not useful for increasing the sealing power of thewax composition. Some I. G. waxes are unsuitable because they cannot beincorporated uniformly into petroleum wax, while the preferred I. G.waxes can be thus uniformly incorporated. When the improved compositionis melted and rapidly cooled in the operation of coating the paper, thepreferred "1. G. waxes do not separate from the petroleum wax or waxes.The composition is either a true and uniform and stable solution of theI. G. wax in the petroleum wax, or auniform and stable dispersion. TheI. G. Wax

E and I. G. Wax B when used in'percentage's less than 1%, impart aslight odor to the wax, but the odor is not detectable in the finalwaxed paper. The I. G. Wax S can also be incorporated uniformly intoparaffin wax so as to form a heat-stable solution or dispersion which isuniform, but it has too much odor for some purposes. Said 8" wax has amelting point of -183 F., an acid value of 142-152, an ester value of25-35, and a very pale yellow color.

These products are used preferably in combination with the fully-refinedpetroleum wax.

The I. G. waxes which may be used for improved self-sealing, and fordecreasing blocking. in addition to I. G. Wax E and I. G. Wax B, are I.G. Wax S (melting-point 180-183 F.), I. G. Wax V (melting-point 122 F.).However, the type which is preferred is the I. G. Wax

E- The B wax has a melting point of 167 F.-

Other I. G. waxes which have been found effective in increasing sealingstrength of paraffin wax are I. G. Wax F. P. and I. G. Wax

K. P. These products have melting points of 175-180 F., acid numbers to35, ester numbers 100 to 125, saponiiication numbers 130-155,unsaponiflable matter 10- 14%, specific gravities 1.0 to 1.03 at 70 F.

In incorporating the I. G-" wax with the usual petroleum wax, the latteris melted in a tank with steam heat to a temperature of 150 to 180 F.The I. G." wax is melted in a separate container and it is added slowlyto the molten petroleum wax while the latter is stirred'mechanically orwhile it is stirred by being blown with air. .The I. G." wax goes intouniform solution or into such a state of uniform dispersion that it doesnot settle out upon standing and solidifying. The mixture is maintainedmolten at 150 F.-180 F. while said solution or dispersion is being made.Petroleum wax which is used forwaxing paper and the like has a range, ofmelting point between 120, F. and 180 F. The difference in melting pointdepends upon the proccess of manufacture and the particular raw materialwhich is used. It is well known that petroleum wax is made commerciallyfrom different fractions of crude petroleum. It is also well known inthe trade that the petroleum wax which is used for waxing bread wrappershas a range of melting point between 125 F. and 140 F- The addition of asmall percentage of I. G." wax, not more than about 2%, to the petroleumwax, does not materially increase the melting point of the petroleumwax.

Specific examples may be given as follows: The petroleum wax used was afully refined product having a melting point of 132 F. (English) and atensile strength of 252 pounds to the square inch at 70F. About 0.5% I.G. Wax E dissolved in the petroleum wax, increased the tensile strengthto 320 pounds, or about 27%, while the sealing strength, as tested bythe methad to be described below, increased 68%. About 0.3% of the I. G.Wax E" increased the sealing strength 39%, while 1.0% of the I. G. Wax Eincreased the sealing strength 92%. These pro- "portions of the I. G.Wax E" are by weight. The percentage of I. G. wax should be small,

not exceeding substantially 2.0%.

The method of making the sealing strength tests were as follows:Sections of a uniform sulphite sheet were waxed respectively with thepetroleum wax alone and with the various mixtures above stated, so thateach section had the same amount of wax per unit of area. Then strips ofsaid sections one inch in width were doubled and each doubled strip waspressed against a beaker containing hot water at a temperature of 190 F.At this temperature, the coating of each doubled strip melted, and thetwo halves of each strip adhered to each other by means of the coating.Then the doubled strips were removed from the surface of the beaker andpermitted to cool in the air. After ageing at room temperature. of '77F. for two hours, the doubled strips were tested as follows: The ends ofeach strip were separated for an inch, one of the separated ends wasthen'inserted into a clamp and the other separated end was attached to athread which extended horizontally over a metal bar and then verticallyto a small cup to which the thread was attached. Bird shot was thenpoured into the cup slowly until the connected parts of the stripstarted to separate or peel apart at a slow rate. The weight of the cupand its contents which was necessary to separate the sealed parts of thestrips, was recorded as the sealing strength.

Another example of the effect of the I. G. Wax E on the sealing strengthof petroleum wax is as follows: The petroleum wax had a tensile strengthof 377 pounds to the square inch at 70 F., and a sealing strength of11.4 gms. When 0.5% of I. G. Wax E" was incorporated in solution withthe petroleum wax, the tensile strength was 460 pounds, an increase of22%, while the sealing strength was 19 gms., an increase of 66%.

In a wax paper plant, paper was waxed on the large machines, first usingstraight petroleum wax, then using a mixture consisting of 99.5%petroleum wax and 0.5% I. G. Wax E." The rolls of paper were then takento a bakery where loaves of bread were wrapped and sealed on thecommercial machines, using both the paper waxed with the straightpetroleum wax and that waxed with said mixture of petroleum wax and I.G. Wax E." Comparing the two products, it was plainly evident that themixture containing the I. G. Wax E was muchstronger than the straightwax.

A'mi'xture of 0.3% wax E," 0.5% amorphous petroleum wax (whose meltingpoint was 160 F.-165 F. by the drop method) and of, fully refinedparaffin wax (petroleum wax) having a 'melting point of 132 F. by theEnglish method,

' composition in the proportion of 0.1% to 10% Whenever I specify aminimum proportion as substantially, I can use less or more than saidminimum proportion. a

In some cases it is desirable to soften the fully refined wax forspecial sheets, in which case-the incorporation of 0.1% to 10% amorphouswax has the desired effect. i

Instead of using amorphous petroleum wax or amorphous paraflin'wax forany of the purposes specified, I can use from 0.1% to 5% of the productknown as Vistanex" instead of using from 0.1% to 10% of said amorphouswax. Said *Vistanex is described in certain patents and publications asfollows:

French Patent No. 740,407; U. S. Patent No. 2,054,115; Rubber Age (NewYork edition) vol. 41, p. 102 (1937). It is prepared by polymerizingiso-olefines, and particularly isobutylene. The molecular weight ofVistanex variesQdepending upon the method of preparation.

The non-amorphous paraflin wax or petroleum wax is melted and kept at atemperature of about 200 F., while the Vistanex" is added in smallpieces with vigorous stirring, until the Vistanex has been uniformlydissolved in or dispersed in the molten wax. The composition is thenallowed to cool and solidify. It is applied-in the molten condition tothe paper, at a temperature of -200 F. It is well known practice tomaintain the temperature of the wax composition above its minimummelting point, when the paper is coated. This is done to render thecomposition more fluid and to increase the penetration of thecomposition into the paper. I therefore use a minimum temperature of 150F., even though the composition may have a lower melting point than 150F. This is well known com-' montanic acid with alcohols. These alcoholsmay be higher alcohols, such as montanyl alcohol. However, said BritishPatent No. 368,425 discloses the use of lower alcohols, such asanhydrous ethyl alcohol. They can be prepared so as to simulate beeswaxand other waxes in certain physical properties. They are described invol. 2, pp. 690 and 691 of the Supplement to Thorpes Dictionary ofApplied Chemistry, published in 1935, (which refers to various technicalpublications which describe said I. G. waxes), and also in vol. 1, p.668 of said supplement.

The glycerol ester of montan wax or of montanic acid also is effectivein increasing the sealing strength of ordinary wax when present in smallpercentages 0.1% to 2.0%.

When I refer to petroleum wax, I include said material if derived fromsources other than petreloum, and analogous waxes.

Likewise, said Britsh Patent No. 368,425 and the other patents referredto therein, disclose products made from carnauba wax and other waxes,which are equivalent to those made from montan wax. Hence, whenever Irefer to montan wax in the claims, I do not exclude equivalent products.

The improved self-sealing coating is substantially free from liquidingredients, so that it is self-sealing when heated and subsequentlycooled, and its ingredients do not separate during th self-sealing.

Besides the esters of montan wax or montanic acid as described above,other polar substances, such as commercial montanic acid itself,carnauba wax and candelilla wax, are effective in increasing sealingstrength when present in small percentages, substantially 0.1% to 2.0%.Montanic acid itself, however, is not as effective as the estersthereof. Therefore the designation polar wax includes esterifiedmontanic acid, commercial montanic acid itself and other polar waxes,preferably those which have at least the polarity of candelilla wax.Likewise, esterifled montanic acid and montanic acid itself areequivalents for the purposes of this invention. The sealing effect ismuch more pronounced in the presence of small percentages of amorphouswax, polymerized isobutylene, ester gum or other resin which is solubleor dispersible in the molten wax.

This application is a continuation in part of my application Serial No.186,978, filed on January 26th, 1938.

A polar substance is understood to be one which contains specialstructural groups, known as polar groups. When the substance is inmolten condition or in solution, the polar groups orient themselvestoward the surface or interface while the hydrocarbon part of themolecule remains buried in the liquid. It is thought that these orientedmolecules attach themselves to the cellulose fibers forming crystalnuclei from which crystals and enhancing the reinforcing effect of ystrength. The polar waxes which I use have at least substantially thepolarity of candelilla wax.

Carnauba wax is more polar than candelilla wax.

The polarity of the wax is tested by the increase in sealing strength. I

The polymerized isobutylene, and the amor- -phous wax, probably act tosome extent as crystal modifiers, in effect increasing the number of thepolar waxes.

The preferred ester of montanic acid is the glycerol ester.

The composition could also include ester gum, or other resin which issoluble or dispersible in the molten petroleum wax, and in theproportion of .5% to 5%.

The montanic acid is a polar compound. Therefore, the montanic acid andthe polar waxes, which include carnauba wax or candelilla wax, areutilized in the composition in the proportion of substantially .1% to2%, amorphous wax can be used in the proportion of substantially .1% to10%, the amorphous wax can be replaced by the polymerized isobutylene inthe proportion of .1% to 5%, and the ester gum or other compatible resincan be used in the proportion of .5% to 5%. These proportions may bebased upon the weight of the entire composition or upon the weight ofthe non-amorphous petroleum wax. The polar substances which are used arerelatively hard and their melting points are higher than F. They aresoluble or dispersible in the petroleum wax at a temperature of F. orabove. The other materials above mentioned, such as the polymerizedisobutylene and the amorphous wax, are softer than the polar substances.Said relatively soft materials are also soluble or dispersible in thepetroleum wax at temperatures above 160 F.

I claim:

1. A solid meltable wax coating composition useful in making waxed paperand having a melting point substantially between 120 F. and F., saidcomposition being substantially free from liquid ingredients and beingself-sealing when heated and subsequently cooled, said compositionincluding a major proportion of petroleum wax and a minor proportion ofa fusible polar wax-like substance selected from the group crystals ofthe polar substance grow throughout and according to the theorydeveloped above, should not be effective in increasing sealingconsisting of montan wax, montanic acid, carnauba wax and candelillawax, the proportion of the fusible polar wax-like substance being atleast substantially 0.1 per cent. of the petroleum wax and not exceedingsubstantially 2 per cent. of the petroleum wax, said fusible polarwax-like substance and the petroleum wax constituting a compatiblemixture which remains stable during said self-sealing.

2. A composition according to claim 1 in which the fusible polarwax-like substance has a melting point which is higher than the meltingpoint of the petroleum wax.

3. A composition according to claim 1 in which the fusible polarwax-like substance has an acid value substantially between 10-152 and anester value which is substantially between 25-155.

4. A composition according to claim 1 in which the melting point of thefusible polar wax-like substance is substantially between 167 F.-183 F.

5. A composition according to claim 1 in which the fusible polarwax-like substance has a melting pointof 167 F.-183 F., an acid value of10- 152 and an ester value of 25-155.

FREDERICK WARDE PADGE'IT.

